Interpositional arthroplasty using cartilage allografts for treating temporomandibular joint arthrosis: a 3- and 5-year retrospective clinical follow-up study.

OBJECTIVE: To evaluate the effect of arthroplasty using interpositional cartilage allografts in patients with temporomandibular joint (TMJ) arthrosis. STUDY DESIGN: This retrospective study included patients treated consecutively between 2007 and 2013 using discectomy and interpositional grafting with lyophilized costal cartilage allograft (Tutoplast) sheets. TMJ pain based on the visual analogue scale (VAS), maximal interincisal opening (MIO), joint tenderness to palpation, crepitus from the affected joint, and postoperative complications were assessed. RESULTS: Arthroplasty was performed on 37 joints among 34 patients (28 women; mean age: 54 years); 24 joints underwent simultaneous condyle shaving. At final follow-up (3 [n = 37] or 5 [n = 21] years), we observed reduced mean VAS (from 7.6 to 0.9; P < .001) increased mean MIO (from 32.5 to 41.1 mm; P < .001), number of joints with capsule tenderness (from 30 to 3; P < .001), and percentage of joints with crepitus (from 97% to 75%; P = .008). One joint required reoperation because of interposed cartilage fragmentation. No permanent facial nerve injury or malocclusion occurred after treatment. CONCLUSIONS: Interpositional arthroplasty is a relatively simple, moderately invasive, and effective surgical treatment for TMJ arthrosis with few complications. However, long-term outcomes of this treatment, specifically beyond 3-5 years postoperatively, remain unknown.

Kinetic Phenomena in Mechanochemical Depolymerization of Poly(styrene).

Synthetic polyolefinic plastics comprise one of the largest shares of global plastic waste, which is being targeted for chemical recycling by depolymerization to monomers and small molecules. One promising method of chemical recycling is solid-state depolymerization under ambient conditions in a ball-mill reactor. In this paper, we elucidate kinetic phenomena in the mechanochemical depolymerization of poly(styrene). Styrene is produced in this process at a constant rate and selectivity alongside minor products, including oxygenates like benzaldehyde, via mechanisms analogous to those involved in thermal and oxidative pyrolysis. Continuous monomer removal during reactor operation is critical for avoiding repolymerization, and promoting effects are exhibited by iron surfaces and molecular oxygen. Kinetic independence between depolymerization and molecular weight reduction was observed, despite both processes originating from the same driving force of mechanochemical collisions. Phenomena across multiple length scales are shown to be responsible for differences in reactivity due to differences in grinding parameters and reactant composition.